Compatible blend systems of oxygen barrier polymers and oxygen scavenging polymers

ABSTRACT

Herein is disclosed an oxygen barrier composition comprising an oxygen barrier polymer and an oxygen scavenging polymer. The composition can be in the form of a physical blend or a cross-linked blend, and can further comprise a compatibilizer, a transesterification catalyst, or both. Preferably, the oxygen barrier polymer is poly(ethylene/vinyl alcohol) (EVOH), polyethylene terephthalate (PET), or polyamide other than MXD6. Preferably, the oxygen scavenging polymer comprises an ethylenic backbone and a pendant cyclic olefinic group, or the oxygen scavenging polymer is a polyamide derived at least in part from a xylene diamine-based monomer.  
     The oxygen barrier composition can be formed into an oxygen barrier layer of a packaging article. Such layers and articles, and methods for making same, are also disclosed.

[0001] This application is a continuation-in-part of application Ser.No. 09/666,642, filed Sep. 21, 2000, which is a continuation-in-part ofapplication Ser. No. 09/595,410, filed Jun. 16, 2000, which is acontinuation-in-part of application Ser. No. 09/575,094, filed May 19,2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to the field of oxygenbarrier polymers. More particularly, it concerns blends of oxygenbarrier polymers, such as poly(ethylene/vinyl alcohol) (EVOH),polyvinyldichloride (PVDC), polyethylene terephthalate (PET), orpolyamide other than MXD6, with oxygen scavenging polymers, methods ofmaking the blends, packaging articles comprising the blends, and methodsof making the packaging articles.

[0004] 2. Description of Related Art

[0005] It is well known that limiting the exposure of oxygen-sensitiveproducts to oxygen maintains and enhances the quality and shelf-life ofthe product. For instance, by limiting the oxygen exposure of oxygensensitive food products in a packaging system, the quality of the foodproduct is maintained, and food spoilage is avoided. In addition suchpackaging also keeps the product in inventory longer, thereby reducingcosts incurred from waste and restocking. In the food packagingindustry, several means for limiting oxygen exposure have already beendeveloped, including modified atmosphere packaging (MAP), vacuumpackaging and oxygen barrier film packaging. In the first two instances,reduced oxygen environments are employed in the packaging, while in thelatter instance, oxygen is physically prevented from entering thepackaging environment.

[0006] Another, more recent, technique for limiting oxygen exposureinvolves incorporating an oxygen scavenger into the packaging structure.Incorporation of a scavenger in the package has been mainly used toremove headspace oxygen within the package in a short period of time,thus the oxygen scavenging polymer typically is based on the polymertype of high oxygen transmission rate, which ensures that the headspaceoxygen in the package quickly reach the oxygen scavenging site and theoxygen level be reduced in a short period of time.

[0007] Oxygen barrier polymers, such as poly(ethylene/vinyl alcohol)(EVOH), polyethylene terephthalate (PET), polyvinyldichloride (PVDC),and polyamide, whether cast, blown, or oriented, are widely known forhaving very strong barrier properties to gases (such as O₂ and CO₂) andother fluids, and have found wide use in packaging applications wherebarrier properties are desired. However, it is generally held that theiroxygen barrier properties are not as strong as those of traditionalpackaging materials, such as glass or metals, which latter materials aresuitable for packaging applications which require high oxygen barrierproperties over a long period of time, such as beer packaging. Thisrequires that the oxygen barrier performance of the existing barrierpolymers be significantly improved or their performance approach tothose of e.g. glass or metals.

[0008] Therefore, it would be desirable to have a packaging articlecomprising an oxygen barrier polymer and an additional component orcomponents, which packaging article would be better suited for providinga high oxygen barrier over a long period of time than are packagingarticles currently known.

[0009] Cochran et al., U.S. Pat. No. 5,021,515, discloses a layer of apackaging article comprising 96% polyethylene terephthalate, 4% nylonMXD6, and 200 ppm cobalt.

[0010] Paleari et al., U.S. Pat. No. 6,063,417, discloses a packagingfilm comprising a core layer comprising about 40 wt% to about 85 wt%nylon 6/12, and about 15 wt% to about 60 wt% ethylene/vinyl alcoholcopolymer (EVOH).

[0011] Koyama et al., U.S. Pat. No. 5,153,038, discloses a packagingarticle comprising a layer comprising an oxygen scavenger, such as apolyhydric phenol, and a gas barrier resin, such as EVOH or polyamide.

[0012] Hong et al., U.S. Pat. No. 5,281,360, discloses a blend of (i) apolymer, such as a formable polyester or polycarbonate; (ii) an oxygenbarrier material, such as EVOH, aromatic or aliphatic nylon, oramorphous nylon (including, according to Hong et al., nylon MXD6); and(iii) a transition metal catalyst. If component (ii) is nylon MXD6, itcan be present up to about 30 wt% of the blend, with component (i)being, preferably, polyethylene terephthalate (PET).

[0013] Collette et al., U.S. Pat. No. 5,759,653, discloses a blend ofPET with an oxygen scavenger, such as nylon MXD6. The blend may alsofurther comprise a metal catalyst.

[0014] Bacskai et al., U.S. Pat. No. 5,641,825, discloses compositionscomprising (i) a polyolefin grafted with an unsaturated carboxylic acidor an unsaturated carboxylic anhydride, (ii) nylon MXD6, and (iii)cobalt as an oxidation catalyst.

SUMMARY OF THE INVENTION

[0015] In one set of embodiments, the present invention relates to acomposition, comprising a blend of an oxygen barrier polymer, an oxygenscavenging polymer, and an oxidation catalyst. The blend can be miscibleor compatible. In one embodiment, the composition can further comprise acompatibilizer. Preferred oxygen barrier polymers include polymers orcopolymers of vinyl alcohol (such as ethylene/vinyl alcohol copolymer(EVOH)), polyesters (such as polyethylene terephthalate (PET) orpolyethylene napthalate (PEN)), polymers or copolymers of vinylidenedichloride (such as polyvinylidene dichloride (PVDC)), polymers orcopolymers of epoxies, polysulfones, polymers or copolymers ofacrylonitrile (such as polyacrylonitrile (PAN)), polymers or copolymersof isocyanates, or polyamides other than MXD6 (e.g. nylon 6; nylon 6,6;or nylon 6,12; among others).

[0016] One preferred oxygen scavenging polymer of the blend is apolyamide derived, at least in part, from monomers comprising xylenediamine moieties, and the blend further comprises a transition metaloxidation catalyst. More preferably, the polyamide is MXD6 polymer oroligomer, and the transition metal catalyst is a cobalt salt with anorganic counterion.

[0017] In a related embodiment, the present invention also relates to apackaging article comprising at least one layer comprising the blend ofthe oxygen barrier polymer and an oxygen scavenging polymer. Thepackaging article can be a single-layer or a multilayer article, and canbe flexible or rigid. A multilayer packaging article can furthercomprise a structural layer or layers, an oxygen barrier layer or layersnot comprising an oxygen scavenging polymer, an oxygen scavenging layer,an oxygen permeable layer or layers, or an adhesive layer or layers,among others.

[0018] In yet another embodiment, the present invention relates to amethod of making the blend of an oxygen barrier polymer and an oxygenscavenging polymer, comprising providing the oxygen barrier polymer andthe oxygen scavenging polymer, and blending the materials. Preferably,the blend comprises an oxidation catalyst, and the providing stepfurther comprises providing the oxidation catalyst. The blending stepcan further comprise enhancing the miscibility or compatibility toimprove the compatibility of the blends by using any suitablecompatibilizer. An oxidation catalyst can be introduced at a suitablestage of the blending process and with a suitable form, either as a neatcatalyst, a solution, or a masterbatch.

[0019] The present invention provides packaging articles that have ahigh oxygen barrier for a long period of time, by taking advantage ofthe inherent oxygen barrier property of e.g. EVOH, PET, PVDC, PAN, orpolyamide other than MXD6 and the oxygen scavenging activity of theoxygen scavenging polymer. Because of the low accessibility of oxygen tothe oxygen scavenging polymer (OSP) on account of the oxygen barrierpolymer, only trace oxygen will reach the OSP; therefore, the OSP istypically not consumed quickly and thus has a very long period of usefullife. The present invention also provides packaging articles having theadvantage of providing a CO₂ barrier (useful in retaining thecarbonation of packaged soft drinks, beer, and sparkling wines) due tothe inherent barrier properties of the barrier resin, as the OSP is onlyincorporated at a level below which the impact on the physical barrierproperties of the oxygen barrier polymer is minimal. Further, a blend ofthe oxygen barrier polymer and the oxygen scavenging polymer typicallyhas good clarity and is readily processible into a variety offormulations. A further advantage is realized when the oxygen barrierpolymer is EVOH and the oxygen scavenging polymer is a polyamide derivedat least in part from xylene diamine-based monomers, viz., EVOH andpolyamides are very likely to be inherently compatible due to afavorable hydrogen bonding interaction between the hydroxyl groups ofEVOH and the amide groups of polyamides, and the further use of acompatibilizer will generally not be required.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0020] Oxygen Barrier Compositions

[0021] In one embodiment, the present invention relates to acomposition, comprising a blend of an oxygen barrier polymer and anoxygen scavenging polymer. Such a composition is useful as a componentof an oxygen barrier layer of a packaging article. By “oxygen barrierlayer” is meant a layer comprising the blend of the oxygen barrierpolymer and the oxygen scavenging polymer. Because of the presence ofthe OSP, the oxygen barrier layer may be referred to as an “activeoxygen barrier” layer.

[0022] Packaging articles typically come in several forms including asingle layer flexible article, a multilayer flexible article, a singlelayer rigid article, or a multilayer rigid article. Typical rigid orsemirigid articles include plastic, paper or cardboard cartons orbottles such as juice containers, soft drink containers, thermoformedtrays, or cups, which have wall thicknesses in the range of 100 to 1000micrometers. Typical flexible articles include those used to packagemany food items, and will likely have a thickness of 5 to 250micrometers. The walls of such articles either comprise single ormultiple layers of material.

[0023] The packaging article comprising the active oxygen barriercomposition can be used to package any product for which it is desirableto inhibit oxygen damage during storage, e.g. food, beverage,pharmaceuticals, medical products, cosmetics, corrodible metals, orelectronic devices. It is especially useful for packaging products forwhich it is desirable to maintain a high oxygen barrier for a longperiod of time, e.g. beer, wine, and other beverages. It is alsoespecially useful for packaging products for which it is desirable toretain carbon dioxide, e.g. beer, sparkling wine, and soft drinks.

[0024] The packaging article comprising the active oxygen barriercomposition can comprise a single layer comprising the composition, oran oxygen barrier layer and additional layers, such as an oxygenscavenging layer, an oxygen barrier layer not comprising an oxygenscavenging polymer, a food-contact layer, a structural layer, or anadhesive layer, alone or in any combination. Single layered packagingarticles can be prepared by solvent casting, injection molding, blowmolding, stretch blow molding, or by extrusion, among other techniques.Packaging articles with multiple layers are typically prepared usingcoextrusion, injection molding, blow molding, stretch blow molding,coating, or lamination, among other techniques.

[0025] The packaging article can comprise any active oxygen barriercomposition described below.

[0026] As stated above, the active oxygen barrier composition comprisesa blend of an oxygen barrier polymer and an oxygen scavenging polymer.Preferably, it further comprises an oxidation catalyst. Preferably, thecomposition, when formed into a film, has an oxygen transmission rate atleast 2 times lower than that of the oxygen barrier polymer alone.

[0027] The oxygen barrier polymer is any polymer generally viewed asproviding a barrier to oxygen passage, e.g. a 1 mil layer consistingessentially of the oxygen barrier polymer has an oxygen transmissionrate of less than about 100 cc/m²/day at room temperature under 1 atm O₂and 0% humidity. Preferably, the oxygen barrier polymer is selected frompolymers or copolymers of vinyl alcohol (such as ethylene/vinyl alcoholcopolymer (EVOH)), polyesters (such as polyethylene terephthalate (PET)or polyethylene napthalate (PEN)), polymers or copolymers of vinylidenedichloride (such as polyvinylidene dichloride (PVDC)), polymers orcopolymers of epoxies, polysulfones, polymers or copolymers ofacrylonitrile (such as polyacrylonitrile (PAN)), polymers or copolymersof isocyanates, or polyamides other than MXD6.

[0028] In one preferred embodiment, the oxygen barrier polymer ispoly(ethylene vinyl alcohol) (EVOH). In still another preferredembodiment, the oxygen barrier polymer is polyacrylonitrile (PAN) or acopolymer comprising acrylonitrile. In a further preferred embodiment,the oxygen barrier polymer is poly(vinylidene dichloride) (PVDC). In yetan additional preferred embodiment, the oxygen barrier polymer ispolyethylene terephthalate (PET). In yet a further preferred embodiment,the oxygen barrier polymer is polyethylene napthalate (PEN). In still anadditional preferred embodiment, the oxygen barrier polymer is apolyamide other than MXD6. The polyamide can be aliphatic or aromatic.Preferred polyamides include nylon 6; nylon 6,6; amorphous polyamide;and nylon 6,12.

[0029] Two or more oxygen barrier polymers can be used. Theappropriateness of a particular oxygen barrier polymer may varydepending on the intended use of the polymer, the composition, or apackaging article made therefrom.

[0030] The oxygen scavenging polymer can be any organic compound thatirreversibly reacts with oxygen. Preferably, the OSP is a thermoplasticthat is miscible or compatible with the oxygen barrier polymer. Thepolymer can be an addition polymer or a condensation polymer. Examplesof addition polymers include, but are not limited to, polymer orcopolymer containing either a main chain or pendant cyclic olefinicgroup, preferably a cyclic olefin group having a cyclohexene structure,such as ethylene/methyl acrylate/cyclohexenylmethyl acrylate terpolymer(EMCM), ethylene/vinyl cyclohexene copolymer (EVCH) orethylene/cyclohexenylmethyl acrylate copolymer (ECHA), orcyclohexenylmethyl acrylate homopolymer (CHAA). Examples also include,but are not limited to, polymer or copolymers containing pendantbenzylic group, such as ethylene/methyl acrylate/benzylmethyl acrylateterpolymer (EMBZ). Examples also include diene polymers such aspolyisoprene, polybutadiene, and copolymers thereof, e.g.styrene-butadiene. Also included are polymeric compounds such aspolypentenamer, polyoctenamer, and other polymers prepared by olefinmetathesis; diene oligomers such as squalene; and polymers or copolymersderived from dicyclopentadiene, norbomadiene, 5-ethylidene-2-norbomene,or other monomers containing more than one carbon-carbon double bond(conjugated or non-conjugated).

[0031] Examples of condensation polymers include, but are not limitedto, condensation polymers such as polyester polymers or copolymerscontaining carbon-carbon double bonds. More preferably, the polyestercontaining either a main chain or a pendant cyclic olefinic groups andcyclic olefinic group, preferably a cyclohexene moiety.

[0032] Preferably, the oxygen scavenging polymer comprises an ethylenicbackbone and at least one cyclic olefinic pendant group. Morepreferably, the cyclic olefinic pendant group is a cycloalkenyl grouphaving the structure I:

[0033] wherein q₁, q₂, q₃, q₄, and r are independently selected fromhydrogen, methyl, or ethyl; m is —(CH₂)_(n)—, wherein n is an integerfrom 0 to 4, inclusive; X is null or a linking group; and, when r ishydrogen, at least one of q₁, q₂, q₃, and q₄ is also hydrogen.Preferably, in structure I, q₁, q₂, q₃, q₄, r, are each hydrogen and mis CH₂ (i.e. the cycloalkenyl group is cyclohexenyl).

[0034] One most preferred oxygen scavenging compound is ethylene/vinylcyclohexene copolymer (EVCH).

[0035] Preferably, X is a linking group linking the ethylenic backboneto the cyclic olefinic group. The linking group is selected from:

[0036]—O—(CHR)_(n)—;—(C═O)—O—(CHR)_(n)—;—NH—(CHR)_(n)—;—O—(C═O)—(CHR)_(n)—;—(C═O)—NH—(CHR)_(n)—; or —(C═O)—O—CHOH—CH₂—O—.

[0037] Preferably, the oxygen scavenging polymer is a homopolymer or acopolymer of cyclohexenylmethyl acrylate. A most preferred oxygenscavenging polymer is ethylene/methyl acrylate/cyclohexenylmethylacrylate terpolymer (EMCM). A further most preferred oxygen scavengingpolymer is ethylene/cyclohexenylmethyl acrylate copolymer (ECHA). Yet afurther most preferred oxygen scavenging polymer is cyclohexenylmethylacrylate homopolymer (CHAA).

[0038] In another embodiment, the oxygen scavenging polymer is apolyester polymer comprising structure II, or structure III:

[0039] wherein q₁, q₂, q₃, q₄, and r are independently selected fromhydrogen, methyl, or ethyl. Preferably, q₁, q₂, q₃, q₄, and r arehydrogen (i.e. the polymer is derived from tetrahydrophthalicanhydride).

[0040] wherein q₁, q₂, q₃, q₄, and r are independently selected fromhydrogen, methyl, or ethyl; m is —(CH₂)_(n)—, wherein n is an integerfrom 0 to 4, inclusive; and, when r is hydrogen, at least one of q₁, q₂,q₃, and q₄ is also hydrogen. Preferably, the polymer is derived from3-cyclohexene-1,1 dimethanol.

[0041] In still another set of preferred embodiments, the oxygenscavenging polymer is a polyamide derived, at least in part, frommonomers comprising a xylene diamine moiety (alternatively, “xylenediamine-based monomers”). By “xylene diamine-based monomer” is meant anysubstituted or unsubstituted xylene diamine wherein the amine groups arecapable of forming polyamide linkages during polymerization with adiacid, diacid halide, etc. The polyamide can be a homopolymer derivedfrom xylene diamine and diacid, or a copolymer comprising any mol % ofmonomers comprising a xylene diamine moiety; preferably, the polyamidecomprises from about 10 mol % to about 50 mol % units derived from axylene diamine-based monomer.

[0042] If the oxygen scavenging polymer is a polyamide derived at leastin part from xylene diamine-based monomers, preferably, the oxygenbarrier polymer is selected from EVOH, PAN, copolymers comprisingacrylonitrile, PVDC, or polyamides not derived from xylene diamine-basedmonomers.

[0043] Two or more oxygen scavenging polymers can be used. It should benoted that the appropriate oxygen scavenging polymer for a given usewill depend on the intended use, its processibility with the oxygenbarrier polymer, and other parameters.

[0044] The blend can comprise from about 0.1% to about 50% of the oxygenscavenging polymer by weight. Preferably, the blend comprises from about1% to about 30% of the oxygen scavenging polymer by weight. The level ofOSP should not significantly plasticize the barrier polymer to cause asignificant lowering in passive barrier properties.

[0045] The blend makes up at least about 50%, preferably at least about80%, by weight of the oxygen barrier composition, with the remaindermade up of other constituents, as described below.

[0046] The blend is preferably in the form of a miscible or compatibleblend. Alternatively, the oxygen scavenging polymer can be present inthe composition as an insoluble filler (i.e. the oxygen scavengingpolymer is cross-linked with itself and is incorporated into the oxygenbarrier polymer matrix as a filler).

[0047] Typically, the blend is a miscible blend, or is made up with theoxygen barrier polymer as a matrix or dispersing phase, with the oxygenscavenging polymer as the dispersed phase.

[0048] From both performance and processing point of view, it istypically desirable that the oxygen scavenging polymer be efficientlydispersed in the barrier polymers. Therefore, a compatibilizer may beneeded to improve the miscibility or compatibility of the blend.

[0049] Preferred compatibilizers include an anhydride-modified oracid-modified poly(ethylene acrylate), poly(ethylene vinyl acetate), orpolyethylene. Another preferred compatibilizer is a block copolymer ofthe oxygen barrier polymer or a polymer similar thereto (such as EVOH,PET, PVDC, polyethylene napthalate (PEN), or polyamide other than MXD6,among others) and EMCM, ECHA, EVCH, CHAA, or a polymer similar thereto(such as another polymer with an ethylenic backbone and a cycloalkenylside chain).

[0050] In the compatibilizer, the blocks of the oxygen barrier polymeror a polymer similar thereto can be linked to the blocks of EMCM, ECHA,EVCH, CHAA, or a polymer similar thereto by any appropriate linkage,such as ester, carbonate, amide, ether, urethane, or urea linkages. Thelinkages can be readily formed by attaching components of the linkage tothe ends of the two different types of blocks, or by forming the linkagefrom components thereof already present at the ends of the two differenttypes of blocks, such as hydroxy and ester components of an esterlinkage such as is used in polyester synthesis. The latter technique canbe used with monomers of the oxygen barrier polymer or polymer similarthereto and the EMCM, ECHA, EVCH, CHAA, or polymer similar thereto, orwith blocks of the two types of monomers. Alternatively, the linkagescan be formed by making monomers or blocks of EMCM, ECHA, EVCH, CHAA, ora polymer similar thereto with reactive end groups, such as hydroxy,ester, or acid end groups, and then blending it with the oxygen barrierpolymer or polymer similar thereto to form block polymers in situ duringblending.

[0051] More preferably, the compatibilizer is a block copolymer of oneof EVOH, PET, PVDC, PEN, or polyamide other than MXD6 with one of EMCM,ECHA, EVCH, or CHAA.

[0052] Acrylic acid-containing compatibilizers can also be used.

[0053] Preferably, the compatibilizer is present in the blend at no morethan about 50% by weight, preferably in the range of about 1 wt % toabout 20 wt %.

[0054] Alternatively, the oxygen scavenging polymer can be renderedinsoluble (meaning “internally cross-linked”) by any appropriatemechanism, e.g. by reacting the oxygen scavenging polymer with achemical crosslinker or by polymerizing the oxygen scavenging polymerwith itself to form a cross-linked structure. The insoluble oxygenscavenging polymer can then be mixed into the oxygen barrier polymerphase as a filler.

[0055] If the oxygen scavenging polymer is a polyamide derived at leastin part from a xylene diamine-based polymer, a compatibilizer istypically not necessary, because polyamides are generally miscible withoxygen barrier polymers. However, one of ordinary skill in the art maywish to include a compatibilizer, in view of the polyamide used, theoxygen barrier polymer used, and other parameters that will be apparent.

[0056] Other compounds are commonly used with oxygen scavengingpolymers, in order to enhance the functionality of the oxygen scavengingpolymers in storage, processing into a layer of a packaging article, oruse of the packaging article. Such enhancements include, but are notlimited to, limiting the rate of oxygen scavenging by the oxygenscavenging polymer prior to filling of the packaging article with aproduct, initiating oxygen scavenging by the oxygen scavenging polymerat a desired time, limiting the induction period (the period betweeninitiating oxygen scavenging and scavenging of oxygen at a desiredrate), or rendering the layer comprising the oxygen scavenging polymerstronger or more transparent, among others. These compounds can be addedto the active oxygen barrier composition comprising the blend of theoxygen barrier polymer and the oxygen scavenging polymer, in order toenhance the functionality of the oxygen scavenging polymer in thecomposition.

[0057] The composition further comprises an oxidation catalyst, such asa transition metal. The transition metal functions to catalyze oxygenscavenging by the oxygen scavenging polymer, increasing the rate ofscavenging and reducing the induction period. Though not to be bound bytheory, useful transition metals include those which can readilyinterconvert between at least two oxidation states. See Sheldon, R. A.;Kochi, J. K.; “Metal-Catalyzed Oxidations of Organic Compounds” AcademicPress, New York 1981.

[0058] Preferably, the transition metal is in the form of a salt, withthe transition metal selected from the first, second or third transitionseries of the Periodic Table. Suitable metals include, but are notlimited to, manganese, iron, cobalt, nickel, copper, rhodium, andruthenium. The oxidation state of the metal when introduced need notnecessarily be that of the active form. The metal is preferably iron,nickel, manganese, cobalt or copper; more preferably manganese orcobalt; and most preferably cobalt. Suitable counterions for the metalinclude, but are not limited to, chloride, acetate, oleate, stearate,palmitate, 2-ethylhexanoate, neodecanoate, or naphthenate; preferably,the counterion is selected from C₁-C₂₀ alkanoates. Preferably, the salt,the transition metal, and the counterion are either on the U.S. Food andDrug Administration GRAS (generally regarded as safe) list, or exhibitsubstantially no migration from the packaging article to the product(i.e. less than about 500 ppb, preferably less than about 50 ppb, in theproduct). Particularly preferable salts include cobalt oleate, cobaltstearate, cobalt 2-ethylhexanoate, and cobalt neodecanoate. The metalsalt may also be an ionomer, in which case a polymeric counterion isemployed. Such ionomers are well known in the art.

[0059] Typically, the amount of transition metal may range from 0.001 to1% (10 to 10,000 ppm) of the composition, based on the metal contentonly (excluding ligands, counterions, etc.). In a packaging article, thetransition metal can be formed in an oxygen barrier layer comprising theoxygen barrier composition of the invention, or in a layer adjacent tothe oxygen barrier layer.

[0060] Another compound that can be added to the composition is aphotoinitiator, or a blend of different photoinitiators. Aphotoinitiator is preferred if antioxidants are included in thecomposition to prevent premature oxidation of the oxygen scavengingpolymer.

[0061] Suitable photoinitiators are well known to those skilled in theart. Specific examples include, but are not limited to, benzophenone,o-methoxybenzophenone, acetophenone, o-methoxy-acetophenone,acenaphthenequinone, methyl ethyl ketone, valerophenone, hexanophenone,α-phenyl-butyrophenone, p-morpholinopropiophenone, dibenzosuberone,4-morpholinobenzophenone, benzoin, benzoin methyl ether,4-o-morpholinodeoxybenzoin, p-diacetylbenzene, 4-aminobenzophenone,4′-methoxyacetophenone, a-tetralone, 9-acetylphenanthrene,2-acetylphenanthrene, 10-thioxanthenone, 3-acetylphenanthrene,3-acetylindole, 9-fluorenone, 1-indanone, 1,3,5-triacetylbenzene,thioxanthen-9-one, xanthene-9-one, 7-H-benz[de]anthracen-7-one, benzointetrahydropyranyl ether, 4,4′-bis(dimethylamino)-benzophenone,1′-acetonaphthone, 2′-acetonaphthone, acetonaphthone and2,3-butanedione, benz[a]anthracene-7,12-dione,2,2-dimethoxy-2-phenylacetophenone, α,α-diethoxyacetophenone, andα,α-dibutoxyacetophenone, among others. Singlet oxygen generatingphotosensitizers such as Rose Bengal, methylene blue, and tetraphenylporphine may also be employed as photoinitiators. Polymeric initiatorsinclude poly(ethylene carbon monoxide) andoligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone].

[0062] Use of a photoinitiator is preferable because it generallyprovides faster and more efficient initiation of oxygen scavenging bythe oxygen scavenging polymer. However, due to the high cost ofphotoinitiators, it is desirable to use the minimum amount ofphotoinitiator required to initiate oxygen scavenging. This minimumamount will vary depending on the photoinitiator used, the wavelengthand intensity of ultraviolet light used to initiate, and other factors.Preferably, the photoinitiator is either on the U.S. Food and DrugAdministration GRAS (generally regarded as safe) list, or exhibitssubstantially no migration from the packaging article to the product(i.e. less than 50 ppb in the product).

[0063] Photoinitiators that are especially useful in the presentinvention include benzophenone derivatives containing at least twobenzophenone moieties, as described in Katsumoto et al., U.S. Pat.6,139,770. These compounds act as effective photoinitiators to initiateoxygen scavenging activity in the oxygen barrier composition of thepresent invention. Such benzophenone derivatives have a very low degreeof extraction from oxygen scavenging compositions, which may lead toreduced malodor or off-taste of a packaged food, beverage, or oralpharmaceutical product by extracted photoinitiator.

[0064] A “benzophenone moiety” is a substituted or unsubstitutedbenzophenone group. Suitable substituents include alkyl, aryl, alkoxy,phenoxy, and alicylic groups contain from 1 to 24 carbon atoms orhalides.

[0065] The benzophenone derivatives include dimers, trimers, tetramers,and oligomers of benzophenones and substituted benzophenones.

[0066] The benzophenone photoinitiators are represented by the formula:

A_(a)(B)_(b)

[0067] wherein A is a bridging group selected from sulfur; oxygen;carbonyl; —SiR″₂—, wherein each R″ is individually selected from alkylgroups containing from 1 to 12 carbon atoms, aryl groups containing 6 to12 carbon atoms, or alkoxy groups containing from 1 to 12 carbon atoms;—NR′″—, wherein R′″ is an alkyl group containing 1 to 12 carbon atoms,an aryl group containing 6 to 12 carbon atoms, or hydrogen; or anorganic group containing from 1 to 50 carbon atoms; a is an integer from0 to 11; B is a substituted or unsubstituted benzophenone group; and bis an integer from 2 to 12.

[0068] The bridging group A can be a divalent group, or a polyvalentgroup with 3 or more benzophenone moieties. The organic group, whenpresent, can be linear, branched, cyclic (including fused or separatecyclic groups), or an arylene group (which can be a fused or non-fusedpolyaryl group). The organic group can contain one or more heteroatoms,such as oxygen, nitrogen, phosphorous, silicon, or sulfur, orcombinations thereof. Oxygen can be present as, for example, an ether,ketone, aldehyde, ester, or alcohol.

[0069] The substituents of B, herein R″, when present, are individuallyselected from alkyl, aryl, alkoxy, phenoxy, or alicylic groupscontaining from 1 to 24 carbon atoms, or halides. Each benzophenonemoiety can have from 0 to 9 substituents. Substituents can be selectedto render the photoinitiator more compatible with the oxygen barriercomposition.

[0070] Examples of such benzophenone derivatives comprising two or morebenzophenone moieties include dibenzoyl biphenyl, substituted dibenzoylbiphenyl, benzoylated terphenyl, substituted benzoylated terphenyl,tribenzoyl triphenylbenzene, substituted tribenzoyl triphenylbenzene,benzoylated styrene oligomer (a mixture of compounds containing from 2to 12 repeating styrenic groups, comprising dibenzoylated 1,1-diphenylethane, dibenzoylated 1,3-diphenyl propane, dibenzoylated 1-phenylnaphthalene, dibenzoylated styrene dimer, dibenzoylated styrene trimer,and tribenzoylated styrene trimer), and substituted benzoylated styreneoligomer. Tribenzoyl triphenylbenzene and substituted tribenzoyltriphenylbenzene are especially preferred.

[0071] When a photoinitiator is used, its primary function is to enhanceand facilitate the initiation of oxygen scavenging by an active oxygenbarrier layer comprising the oxygen scavenging polymer upon exposure toradiation. The amount of photoinitiator can vary. In many instances, theamount will depend on the blend ratio or the particular oxygenscavenging polymer used, the wavelength and intensity of UV radiationused, the nature and amount of antioxidants used, as well as the type ofphotoinitiator used. The amount of photoinitiator also depends on theintended use of the composition. For instance, if thephotoinitiator-containing component is placed underneath a layer whichis somewhat opaque to the radiation used, more initiator may be needed.For most purposes, however, the amount of photoinitiator, when used,will be in the range of 0.01 to 10% by weight of the oxygen barriercomposition.

[0072] Antioxidants can be used in the composition to control scavenginginitiation. An antioxidant as defined herein is a material whichinhibits oxidative degradation or cross-linking of polymers. Typically,antioxidants are added to facilitate the processing of polymericmaterials or prolong their useful lifetime. In relation to thisinvention, such additives prolong the induction period for oxygenscavenging in the absence of irradiation. When it is desired to commenceoxygen scavenging by the oxygen scavenging polymer of the active oxygenbarrier layer of the packaging article, the packaging article (and anyincorporated photoinitiator) can be exposed to radiation.

[0073] Antioxidants such as 2,6-di(t-butyl)-4-methylphenol(BHT),2,2′-methylene-bis(6-t-butyl-p-cresol), triphenylphosphite,tris-(nonylphenyl)phosphite, vitamin E, tetra-bismethylene3-(3,5-ditertbutyl-4-hydroxyphenyl)-propionate methane, anddilaurylthiodipropionate are suitable for use with this invention.

[0074] The amount of an antioxidant which may be present may also havean effect on oxygen scavenging. As mentioned earlier, such materials areusually present in oxidizable organic compounds or structural polymersto prevent oxidation or gelation of the polymers. Typically, they arepresent in about 0.01 to 1% by weight of the composition. However,additional amounts of antioxidant may also be added if it is desired totailor the induction period as described above.

[0075] Other additives which can be included in the active oxygenbarrier layer include, but are not necessarily limited to, fillers,pigments, dyestuffs, stabilizers, processing aids, plasticizers, fireretardants, and anti-fog agents, among others.

[0076] Any other additives employed normally will not comprise more than10% of the composition by weight, with preferable amounts being lessthan 5% by weight of the composition.

[0077] The active oxygen barrier composition can be stored after beingmade, or can be made as part of a process of forming a packagingarticle, as will be described below.

[0078] In addition to the active oxygen barrier layer, if the packagingarticle is a multilayer article, it can comprise other layers useful ina flexible or rigid multilayer packaging article.

[0079] As stated above, if a transition metal salt is included in thepackaging article to increase the rate of oxygen scavenging or reducethe induction time, the transition metal can be included either in theactive oxygen barrier layer or in a layer adjacent to the active oxygenbarrier layer. Any transition metal salt described above can be formedin the adjacent layer.

[0080] The active oxygen barrier layer can also comprise aphotoinitiator, an antioxidant, or both, as described above. Otheradditives can also be included as desired.

[0081] A multilayer packaging article of the present invention can alsocomprise at least one structural layer located to the interior, theexterior, or both of the active oxygen barrier layer. The structurallayer or layers comprise a structural polymer that imparts usefulstructural properties, such as rigidity, flexibility, or strength, amongothers, to the packaging article. Suitable structural polymers include,but are not limited to, polyethylene, low density polyethylene, very lowdensity polyethylene, ultra-low density polyethylene, high densitypolyethylene, polyvinyl chloride, ethylene-vinyl acetate, ethylene-alkyl(meth)acrylates, ethylene-(meth)acrylic acid, PET, polyamides,polypropylene, or ethylene-(meth)acrylic acid ionomers. Blends ofdifferent structural polymers may also be used. However, the selectionof the structural polymer largely depends on the article to bemanufactured and the end use thereof. Such selection factors are wellknown in the art.

[0082] Preferably, the structural polymer is selected from PET,polyamides, polypropylene, polyethylene, low density polyethylene, verylow density polyethylene, ultra-low density polyethylene, high densitypolyethylene, polyvinyl chloride, ethylene-vinyl acetate, ethylene-alkyl(meth)acrylates, ethylene-(meth)acrylic acid, or ethylene-(meth)acrylicacid ionomers.

[0083] If the packaging article is a rigid carton, such as a juicecarton, the structural layer can comprise paperboard or cardboard.

[0084] Also, a multilayer packaging article may comprise an oxygenscavenging layer, comprising an oxygen scavenging polymer and,optionally, other additives, such as a photoinitiator, a transitionmetal catalyst, an antioxidant, a structural polymer, or others, aloneor in any combination, as described above. The oxygen scavenging layercan be an integral part of the packaging article, or it can be a liner,coating, sealant, gasket, adhesive, non-adhesive insert, or fibrous matinsert in the packaging article.

[0085] Additionally, a multilayer packaging article according to thepresent invention may further comprise at least one oxygen barrierlayer, i.e. a layer having an oxygen transmission rate equal to or lessthan 100 cubic centimeters per square meter (cc/m²) per day peratmosphere at room temperature (about 25° C.) and 0% humidity, whereinthe layer does not comprise an oxygen scavenging polymer. Typical oxygenbarrier layers comprise poly(ethylene/vinyl alcohol) (EVOH),polyacrylonitrile, a copolymer comprising acrylonitrile, poly(vinylidenedichloride), polyethylene terephthalate (PET), silica, polyamide otherthan MXD6, or mixtures thereof. However, because the blend of the oxygenbarrier polymer and the oxygen scavenging polymer inhibits oxygentransmission to a high degree, the need for a separate oxygen barrierlayer is reduced and may, depending on the form of the packaging articleand the intended use, be dispensed with entirely, if desired.

[0086] Other additional layers of a multilayer packaging article mayinclude one or more layers which are permeable to oxygen. In onepackaging article, preferred for flexible packaging of food andscavenging of oxygen found in the packaged food, the layers include, inorder starting from the outside of the package to the innermost layer ofthe package, (i) an oxygen barrier layer, (ii) an optional oxygenscavenging layer, and (iii) an optional oxygen-permeable layer. Controlof the oxygen barrier property of (i) limits the rate of oxygen entry tothe oxygen scavenging moieties in layer (ii), and thus slows theconsumption of oxygen scavenging capacity by atmospheric oxygen. Controlof the oxygen permeability of layer (iii) impacts the rate of oxygenscavenging for the overall structure. Furthermore, layer (iii) canprovide a barrier to migration of the components of the outer layers, orby-products of the reaction of such components with oxygen or otherreactants, into the package interior. Even further, layer (iii) canimprove the heat-sealability, clarity, or resistance to blocking of themultilayer packaging article.

[0087] Further additional layers, such as adhesive layers, may also beused in the multilayer packaging article. Compositions typically usedfor adhesive layers include anhydride functional polyolefins and otherwell-known adhesive layers.

[0088] In another embodiment, the present invention relates to a methodof making an active oxygen barrier composition comprising an oxygenbarrier polymer and an oxygen scavenging polymer, comprising blendingthe oxygen barrier polymer and the oxygen scavenging polymer.

[0089] The oxygen barrier polymer and the oxygen scavenging polymer areas described above. Typically, the oxygen barrier polymer and the oxygenscavenging polymer are provided as a solid formulation, such as pelletsor a powder.

[0090] The blend can be prepared by mixing the oxygen barrier polymerand the oxygen scavenging polymer in any appropriate apparatus.Typically, the oxygen barrier polymer and the oxygen scavenging polymerare mixed together, heated to melting and stirred to homogeneity, andthe homogenous melt is then extruded. The extruded melt is thentypically cooled and pelletized to form pellets of the blend. However,other forms of the blend, such as a powder, are possible. Othertechniques of preparing the blend may be apparent to one of ordinaryskill in the art.

[0091] To aid mixing of the oxygen barrier polymer and the oxygenscavenging polymer, the blending step can further comprise blending acompatibilizer with the oxygen barrier polymer and the oxygen scavengingpolymer. The compatibilizer is as described above. The blending can alsointegrated directed into the manufacturing process or forming step ofthe final packaging article as the feed material.

[0092] Alternatively, if the oxygen scavenging polymer is desired as afiller in the oxygen barrier polymer phase, then the composition can beprepared by, first, internally cross-linking the oxygen scavengingpolymer, such as by chemical cross-linking or polymerization, andsecond, mixing the insoluble oxygen scavenging polymer with the oxygenbarrier polymer.

[0093] The blend can also comprise other constituents, such as atransition metal oxidation catalyst, a photoinitiator, an antioxidant,or any combination thereof, among others, as described above. Theconstituents can generally be added to the blending step. If the OSP isprovided as a filler, the constituents are typically blended with theoxygen barrier polymer phase. The oxidation catalyst can be introducedat any stage of the process, either at the mixing stage or at thefabrication stage of the final article, see below.

[0094] After being made, the blend can be stored for at least severaldays, and preferably indefinitely, or it can be made as part of a methodof forming an oxygen barrier layer in a packaging article, as describedbelow. In such a method, the blended composition is fed from theextruder or other blending apparatus directly into further steps of themethod.

[0095] In another embodiment, the present invention relates to a methodof forming an active oxygen barrier layer in a packaging article,comprising: (i) providing an oxygen barrier composition comprising anoxygen barrier polymer and an oxygen scavenging polymer; and (ii)forming the composition into the packaging article or the oxygen barrierlayer thereof.

[0096] The packaging article can be flexible or rigid, single-layer ormultilayer, as described above. The oxygen barrier polymer and theoxygen scavenging polymer are also as described above. Preferably, theoxygen scavenging polymer comprises an ethylenic backbone and acycloalkenyl group having structure I:

[0097] wherein q₁, q₂, q₃, q₄, and r are independently selected fromhydrogen, methyl, or ethyl; m is —(CH₂)_(n)—, wherein n is an integerfrom 0 to 4, inclusive; X is null or a linking group; and, when r ishydrogen, at least one of q₁, q₂, q₃, and q₄ is also hydrogen.Preferably, in structure I, q₁, q₂, q₃, q₄, r, are each hydrogen and nis 1 (i.e. the cycloalkenyl group is cyclohexenyl).

[0098] One most preferred oxygen scavenging compound is ethylene/vinylcyclohexene copolymer (EVCH).

[0099] Preferably, X is a linking group linking the ethylenic backboneto the cyclic olefinic group. The linking group is selected from:

[0100]—O—(CHR)_(n)—;—(C═O)—O—(CHR)_(n)—;—NH—(CHR)_(n)—;—O—(C═O)—(CHR)_(n)—;—(C═O)—NH—(CHR)_(n)—; or —(C═O)—O—CHOH—CH₂—O—.

[0101] Preferably, the oxygen scavenging polymer is a homopolymer or acopolymer of cyclohexenylmethyl acrylate. A most preferred oxygenscavenging polymer is ethylene/methyl acrylate/cyclohexenylmethylacrylate terpolymer (EMCM). A further most preferred oxygen scavengingpolymer is ethylene/cyclohexenylmethyl acrylate copolymer (ECHA). Yet afurther most preferred oxygen scavenging polymer is cyclohexenylmethylacrylate homopolymer (CHAA).

[0102] In another embodiment, the oxygen scavenging polymer is apolyester polymer comprising structure II or structure III:

[0103] wherein q₁, q₂, q₃, q₄, and r are independently selected fromhydrogen, methyl, or ethyl. Preferably, q₁, q₂, q₃, q₄, and r arehydrogen (i.e. the monomer is tetrahydrophthalic anhydride).

[0104] wherein q₁, q₂, q₃, q₄, and r are independently selected fromhydrogen, methyl, or ethyl; m is —(CH₂)_(n)—, wherein n is an integerfrom 0 to 4, inclusive; and, when r is hydrogen, at least one of q₁, q₂,q₃, and q₄ is also hydrogen. Preferably, the monomer is3-cyclohexene-l,l dimethanol (i.e. q₁, q₂, q₃, q_(4,) and r are hydrogenand n is 1).

[0105] Still another preferred oxygen scavenging polymer is EMBZ, asdiscussed above.

[0106] In an alternative embodiment, preferably the oxygen scavengingpolymer is a polyamide derived, at least in part, from xylenediamine-based monomers.

[0107] The packaging article may comprise one or more oxygen barrierlayers comprising the composition of the present invention.

[0108] The forming step can be by any technique appropriate depending onthe oxygen barrier composition, the packaging article, and otherparameters. As mentioned above, single layered packaging articlestypically can be prepared by solvent casting, injection molding, blowmolding, injection blow molding, or extrusion, among others. Packagingarticles with multiple layers are typically prepared using coextrusion,injection molding, blow molding, injection blow molding, coating, orlamination, among others.

[0109] If a transition metal catalyst is desired for inclusion in thepackaging article, to catalyze oxygen scavenging by the composition, theforming step comprises forming a transition metal catalyst into theoxygen barrier layer or a layer adjacent to the oxygen barrier layer ofthe packaging article.

[0110] The active oxygen barrier composition can also comprise aphotoinitiator, an antioxidant, a structural polymer, or other additivesas described above.

[0111] In addition to the active oxygen barrier layer, the packagingarticle to be formed can comprise other layers, such as an oxygenbarrier layer not comprising an oxygen scavenging polymer, a structurallayer, an oxygen scavenging layer, or a seal layer or food contact layerforming the interior surface of the packaging article, among others.Depending on the desired form of the packaging article, the forming stepcan comprise forming the packaging article as a single layer flexiblearticle, a multilayer flexible article, a single layer rigid article, ora multilayer rigid article.

[0112] The following examples are included to demonstrate preferredembodiments of the invention. It should be appreciated by those of skillin the art that the techniques disclosed in the examples which followrepresent techniques discovered by the inventor to function well in thepractice of the invention, and thus can be considered to constitutepreferred modes for its practice. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments which are disclosed and stillobtain a like or similar result without departing from the spirit andscope of the invention.

EXAMPLE 1 Preparation of a Multi-Layer Film with an Oxygen Barrier CoreLayer

[0113] A series of four dry blend samples were prepared from pellets ofethylene-vinyl alcohol copolymer (EVOH), ethylene/methylacrylate/cyclohexenylmethyl acrylate terpolymer (EMCM), and anethylene/methyl acrylate copolymer-(EMAC-) based cobalt masterbatch(containing 1 wt % tribenzoyl triphenylbenzene (BBP³) and 1 wt % cobaltas cobalt oleate) by mixing in a polyethylene bag. The samples differedin the weight ratio among EVOH, EMCM, and the cobalt masterbatch. Afifth sample consisting of EVOH was prepared as a control. Theproportions of the ingredients in the blends are shown in Table 1. TABLE1 Blend Composition EVOH, EMCM Masterbatch Material % by wt. % by wt. %by wt. Sample 1 95 4.5 0.5 Sample 2 90 9 1 Sample 3 87 9 4 Sample 4 8018 2 Sample 5 100 0 0

[0114] The EVOH (Soarnol A4412 grade, from Nippon Synthetic ChemicalIndustry Co.) used contained 44 mole % ethylene content and had a meltindex of 12 g/10 min at 210° C. and a loading of 2.16 kg, and a meltingpoint of 164° C. The EVOH resin was dried at 90° C. for 3 hours undervacuum to remove residual moisture.

[0115] EMCM, the oxygen scavenging polymer used, was as discussed in theprevious section, and was obtained from Chevron Chemical Co.

[0116] The EMAC-based cobalt masterbatch (containing 1 wt % BBP³ and 1wt % cobalt as cobalt oleate) was obtained from Chevron Chemical Co.

[0117] The above four dry blends and the control (Samples 1-5) were meltblended on a Hakke twin screw extruder at temperature range of 190° C.to 220° C. at 30 rpm screw speed. A three layer film was cast from eachcomposition from a Randcastle coextrusion machine, with the oxygenbarrier blend composition or control as core layer and commercialpolyethylene as interior and exterior skin layers. The dimension of thethree layer films was controlled at 0.5 mil/1.0 mil/0.5 mil. Thetemperature settings for film casting were in the range of 430° F. andscrew speeds were in the range of 15 rpm to 30 rpm. The material of eachindividual layer was fed into one of the two extruders of the Randcastlemachine. While in the die, the layers were juxtaposed and combined, thenemerged from the die as a three-layer film. After exiting the die, thefilm was oriented monoaxially: the extrudate was cast onto a firstcontrolled temperature casting roll with stretching in the machinedirection and the film was then collected at the second roll. All thefilms made were transparent with light color.

EXAMPLE 2 Oxygen Transmission Test on Mocon

[0118] The films prepared in Example 1 were tested for oxygenpermeability using a Mocon Ox-Trans 2/20 ML system at 23° C. Nitrogencontaining 2% hydrogen was used as carrier gas to flush both sides ofthe film at 10 cc/min flow rate for 1-4 hrs before testing. Air was usedas test gas at 10 cc/min flow rate. The oxygen permeability was measuredin cubic centimeters per square meter per 24 hours. The film size forthe test was 50 cm². Oxygen scavenging by EMCM in the oxygen barrierlayer was triggered by exposing the film to UV light at 254 nm. TABLE 2Oxygen Permeability Oxygen EVOH, EMCM Masterbatch Permeability Material% by wt. % by wt. % by wt. cc/m² · day Sample 1 95 4.5 0.5 — Sample 2 909 1 4.16 Sample 3 87 9 4 0.62 Sample 4 80 18 2 0.0 Sample 5 100 0 0 4.64

[0119] From the above table, it is apparent that the presence of theoxygen scavenging polymer EMCM in the EVOH matrix (i.e. having an activeoxygen barrier) can significantly lower the oxygen permeability of afilm, relative to films comprising oxygen barrier layers not comprisingan oxygen scavenging polymer as are known in the art. At 9 wt % loadingof EMCM (sample 3), the oxygen permeability was lowered about 7-foldwith the presence of sufficient cobalt masterbatch. At 18 wt % loadingof EMCM, the oxygen permeability was lowered to substantially zero.

EXAMPLE 3 Preparation of a Multi-Layer Film with an Oxygen Barrier CoreLayer

[0120] A series of three dry blend samples were prepared from pellets ofethylene-vinyl alcohol copolymer (EVOH, Eval F101A, containing 68% molevinyl alcohol, from Evalca Co.), MXD6 Nylon (MX Nylon 6007 fromMitsubishi Gas Chemical Co.) and an ethylene/methyl acrylatecopolymer-(EMAC) based cobalt masterbatch (containing 1 wt % cobalt ascobalt oleate), by mixing in a polyethylene bag. The samples differed inthe weight ratio among EVOH, MXD6, and the cobalt catalyst masterbatch.The proportions of the ingredients in the blends, as well as the corelayer composition of 3-layer films, are shown in Table 3. TABLE 3 BlendComposition of Core Layer in 3-Layered Films: Co Masterbatch MaterialEVOH, % wt. MXD6, % wt. % wt. Sample 1 100 0 0 Sample 2 95 5 0 Sample 394 5 1

[0121] The two formulations (sample 2-3) were melt blended on an Haaketwin screw extruder at temperature 260° C. at 20 rpm screw speed. The3-layer film samples were then cast on a Randcastle coextrusion machine,with each of the above formulations (sample 1-3) as core layer andpolyethylene resin (Chevron PE 4517) as skin layer. The layer structurewas as PE/sample/PE (1.0/1.0/1.0 mil). On the Randcastle machine, thetemperature settings were 460° F., 510° F. and 520° F. for zones 1-3,respectively. The screw speed was set at 40 rpm. The temperature was setat 510° F. for the feed block and 500° F. for the die. After exiting thedie, the film was oriented monoaxially: the extrudate was cast onto afirst controlled temperature casting roll with stretching in the machinedirection and the film was then collected at the second roll. All thefilms made were transparent, an indication of sufficient compatibilityof the blends.

EXAMPLE 4 Oxygen Transmission Test on Mocon Oxtran

[0122] The films prepared in Example 3 were tested for oxygenpermeability using a Mocon Ox-Trans 2/20 system at 23° C. under dryconditions. Nitrogen containing 2% hydrogen was used as carrier gas toflush both sides of the film at 10 cc/min flow rate for 1-4 hrs beforetesting. Air was used as test gas at 10 cc/min flow rate. The oxygenpermeability was measured in cubic centimeters per square meter per 24hours. The film size for the test is 50 cm².

[0123] Table 4. Oxygen Transmission Rate vs. Core Layer Composition of3-Layer Films: OTR, Core Layer EVOH, Co Masterbatch cc/ Composition %wt. MXD6, % wt. % wt. mil.M²·Day Sample 1 100 0 0 0.54 Sample 2 95 5 00.46 Sample 3 94 5 1 0

[0124] From the above table, it is apparent that the presence of theoxygen scavenging polymer MXD6, along with small amount of cobaltcatalyst, in the EVOH matrix can significantly lower the oxygenpermeability of a film, relative to films comprising oxygen barrierlayers not comprising an oxygen scavenging polymer as are known in theart. At 5 wt % loading of MXD6 (sample 3), the oxygen permeability wasreduced below the detection limit with the presence of a very smallamount of cobalt masterbatch.

[0125] All of the compositions and methods disclosed and claimed hereincan be made and executed without undue experimentation in light of thepresent disclosure. While the compositions and methods of this inventionhave been described in terms of preferred embodiments, it will beapparent to those of skill in the art that variations may be applied tothe compositions and methods and in the steps or in the sequence ofsteps of the method described herein without departing from the concept,spirit and scope of the invention. More specifically, it will beapparent that certain agents which are both chemically andphysiologically related may be substituted for the agents describedherein while the same or similar results would be achieved. All suchsimilar substitutes and modifications apparent to those skilled in theart are deemed to be within the spirit, scope and concept of theinvention as defined by the appended claims.

What is claimed is:
 1. An oxygen barrier composition, comprising: aoxygen barrier polymer, an oxygen scavenging polymer, and an oxidationcatalyst, wherein the oxygen barrier polymer is selected frompoly(ethylene/vinyl alcohol) (EVOH), polyacrylonitrile (PAN), copolymerscomprising acrylonitrile, poly(vinylidene dichloride) (PVDC), orpolyamides not derived from xylene diamine-based monomers; and theoxygen scavenging polymer is a polyamide oligomer or polymer derived atleast in part from a xylene diamine-based monomer.
 2. The composition ofclaim 1, wherein the oxygen scavenging polymer comprises from about 10mol % to about 50 mol % units derived from a xylene diamine-basedmonomer.
 3. The composition of claim 1, wherein the oxygen scavengingpolymer comprises from about 1% to about 30% of the blend by weight. 4.The composition of claim 1, wherein the oxygen scavenging polymer isMXD6.
 5. The composition of claim 1, wherein the composition has anoxygen transmission rate at least 2 times lower than that of the oxygenbarrier polymer alone.
 6. The composition of claim 1, wherein theoxidation catalyst comprises a transition metal selected from cobalt,copper, nickel, iron, manganese, rhodium, or ruthenium.
 7. Thecomposition of claim 6, wherein the oxidation catalyst is a saltcomprising a counterion selected from C₁-C₂₀ alkanoates.
 8. Thecomposition of claim 7, wherein the transition metal salt is cobaltoleate, cobalt stearate, or cobalt neodecanoate.
 9. The composition ofclaim 1, further comprising a photoinitiator.
 10. The composition ofclaim 9, wherein the photoinitiator is selected from benzophenonederivatives containing at least two benzophenone moieties and having theformula: A_(a)(B)_(b) wherein A is a bridging group selected fromsulfur; oxygen; carbonyl; —SiR″₂—, wherein each R″ is individuallyselected from alkyl groups containing from 1 to 12 carbon atoms, arylgroups containing 6 to 12 carbon atoms, or alkoxy groups containing from1 to 12 carbon atoms; —NR′″—, wherein R′″ is an alkyl group containing 1to 12 carbon atoms, an aryl group containing 6 to 12 carbon atoms, orhydrogen; or an organic group containing from 1 to 50 carbon atoms; a isan integer from 0 to 11; B is a substituted or unsubstitutedbenzophenone group; and b is an integer from 2 to
 12. 11. Thecomposition of claim 10, wherein the photoinitiator is selected fromdibenzoyl biphenyl, substituted dibenzoyl biphenyl, benzoylatedterphenyl, substituted benzoylated terphenyl, tribenzoyltriphenylbenzene, substituted tribenzoyl triphenylbenzene, benzoylatedstyrene oligomer, or substituted benzoylated styrene oligomer.
 12. Thecomposition of claim 1, further comprising an antioxidant.
 13. Thecomposition of claim 12, wherein the antioxidant is selected from2,6-di(t-butyl)-4-methylphenol(BHT),2,2′-methylene-bis(6-t-butyl-p-cresol), triphenylphosphite,tris-(nonylphenyl)phosphite, vitamin E, tetra-bismethylene3-(3,5-ditertbutyl-4-hydroxyphenyl)-propionate methane, ordilaurylthiodipropionate.
 14. A packaging article, comprising: at leastone oxygen barrier layer comprising an oxygen barrier polymer and anoxygen scavenging polymer, wherein the oxygen barrier polymer isselected from poly(ethylene/vinyl alcohol) (EVOH), polyacrylonitrile(PAN), copolymers comprising acrylonitrile, poly(vinylidene dichloride)(PVDC), or polyamides not derived from xylene diamine-based monomers;and the oxygen scavenging polymer is a polyamide oligomer or polymerderived at least in part from a xylene diamine-based monomer.
 15. Thepackaging article of claim 14, wherein the oxygen scavenging polymercomprises from about 10 mol % to about 50 mol % units derived from axylene diamine-based monomer.
 16. The packaging article of claim 14,wherein the oxygen scavenging polymer comprises from about 1% to about30% of the blend by weight.
 17. The packaging article of claim 14,wherein the oxygen scavenging polymer is MXD6.
 18. The packaging articleof claim 14, further comprising a transition metal salt in the oxygenbarrier layer or a layer adjacent to the oxygen barrier layer.
 19. Thepackaging article of claim 18, wherein the transition metal is selectedfrom cobalt, copper, nickel, iron, manganese, rhodium, or ruthenium. 20.The packaging article of claim 19, wherein the transition metal saltcomprises a counterion selected from C₁-C₂₀ alkanoates.
 21. Thepackaging article of claim 20, wherein the transition metal salt iscobalt oleate, cobalt stearate, or cobalt neodecanoate.
 22. Thepackaging article of claim 14, further comprising a photoinitiator inthe oxygen barrier layer.
 23. The packaging article of claim 22, whereinthe photoinitiator is selected from benzophenone derivatives containingat least two benzophenone moieties and having the formula: A_(a)(B)_(b)wherein A is a bridging group selected from sulfur; oxygen; carbonyl;—SiR″2—, wherein each R″ is individually selected from alkyl groupscontaining from 1 to 12 carbon atoms, aryl groups containing 6 to 12carbon atoms, or alkoxy groups containing from 1 to 12 carbon atoms;—NR′″—, wherein R′″ is an alkyl group containing 1 to 12 carbon atoms,an aryl group containing 6 to 12 carbon atoms, or hydrogen; or anorganic group containing from 1 to 50 carbon atoms; a is an integer from0 to 11; B is a substituted or unsubstituted benzophenone group; and bis an integer from 2 to
 12. 24. The packaging article of claim 23,wherein the photoinitiator is selected from dibenzoyl biphenyl,substituted dibenzoyl biphenyl, benzoylated terphenyl, substitutedbenzoylated terphenyl, tribenzoyl triphenylbenzene, substitutedtribenzoyl triphenylbenzene, benzoylated styrene oligomer, orsubstituted benzoylated styrene oligomer.
 25. The packaging article ofclaim 14, further comprising an antioxidant in the oxygen barrier layer.26. The packaging article of claim 25, wherein the antioxidant isselected from 2,6-di(t-butyl)-4-methylphenol(BHT),2,2′-methylene-bis(6-t-butyl-p-cresol), triphenylphosphite,tris-(nonylphenyl)phosphite, vitamin E, tetra-bismethylene3-(3,5-ditertbutyl-4-hydroxyphenyl)-propionate methane, ordilaurylthiodipropionate.
 27. The packaging article of claim 14, furthercomprising an oxygen barrier layer, wherein the oxygen barrier layerdoes not comprise a polyamide derived at least in part from a xylenediamine-based monomer.
 28. The packaging article of claim 27, whereinthe oxygen barrier layer not comprising a polyamide derived at least inpart from a xylene diamine-based monomer comprises poly(ethylene vinylalcohol) (EVOH), polyacrylonitrile (PAN), a copolymer comprisingacrylonitrile, poly(vinylidene dichloride) (PVDC), polyethyleneterephthalate (PET), polyethylene napthalate (PEN), or polyamide otherthan MXD6.
 29. The packaging article of claim 14, further comprising astructural layer.
 30. The packaging article of claim 29, wherein thestructural layer comprises PET, polyamide, polypropylene, polyethylene,low density polyethylene, very low density polyethylene, ultra-lowdensity polyethylene, high density polyethylene, polyvinyl chloride,ethylene-vinyl acetate, ethylene-alkyl (meth)acrylates,ethylene-(meth)acrylic acid, ethylene-(meth)acrylic acid ionomers,paperboard, or cardboard.
 31. The packaging article of claim 14, furthercomprising an oxygen scavenging layer.
 32. The packaging article ofclaim 31, wherein the oxygen scavenging layer comprises an oxygenscavenging polymer comprising an ethylenic backbone and a cycloalkenylgroup with structure I:

wherein q₁, q₂, q₃, q₄, and r are independently selected from hydrogen,methyl, or ethyl; m is —(CH₂)_(n)—, wherein n is an integer from 0 to 4,inclusive; and, when r is hydrogen, at least one of q₁, q₂, q₃, and q₄is also hydrogen.
 33. The packaging article of claim 32, wherein theoxygen scavenging layer comprises an oxygen scavenging polymer selectedfrom ethylene/methyl acrylate/cyclohexenylmethyl acrylate terpolymer(EMCM), ethylene/vinyl cyclohexene copolymer (EVCH),ethylene/cyclohexenylmethyl acrylate copolymer (ECHA), orcyclohexenylmethyl acrylate homopolymer (CHAA).
 34. The packagingarticle of claim 31, wherein the oxygen scavenging layer is a liner,coating, sealant, gasket, adhesive, non-adhesive insert, or fibrous matinsert in the packaging article.
 35. The packaging article of claim 14,wherein the packaging article is in the form of a single layer flexiblearticle, a multilayer flexible article, a single layer rigid article, ora multilayer rigid article.
 36. A method of making an oxygen barriercomposition comprising an oxygen barrier polymer, an oxygen scavengingpolymer, and an oxidation catalyst, wherein the oxygen barrier polymeris selected from poly(ethylene/vinyl alcohol) (EVOH), polyacrylonitrile(PAN), copolymers comprising acrylonitrile, poly(vinylidene dichloride)(PVDC), or polyamides not derived from xylene diamine-based monomers;and the oxygen scavenging polymer is a polyamide oligomer or polymerderived at least in part from a xylene diamine-based monomer: providingthe oxygen barrier polymer, the polyamide derived at least in part froma xylene diamine-based monomer, and the oxidation catalyst; and blendingthe oxygen barrier polymer, the polyamide, and the oxidation catalyst,to form the oxygen barrier composition.
 37. The method of claim 36,wherein the oxygen scavenging polymer comprises from about 1% to about30% of the blend by weight.
 38. The method of claim 36, wherein theoxygen scavenging polymer is MXD6.
 39. The method of claim 36, whereinthe blending occurs during a reactive extrusion.
 40. A method of formingan oxygen barrier layer in a packaging article, comprising: providing anoxygen barrier composition comprising an oxygen barrier polymer and anoxygen scavenging polymer, wherein the oxygen barrier polymer isselected from poly(ethylene/vinyl alcohol) (EVOH), polyacrylonitrile(PAN), copolymers comprising acrylonitrile, poly(vinylidene dichloride)(PVDC), or polyamides not derived from xylene diamine-based monomers;and the oxygen scavenging polymer is a polyamide oligomer or polymerderived at least in part from a xylene diamine-based monomer; andforming the composition into the packaging article or an oxygen barrierlayer thereof.
 41. The method of claim 40, wherein the oxygen scavengingpolymer comprises from about 1% to about 30% of the composition byweight.
 42. The method of claim 40, wherein the oxygen scavengingpolymer is MXD6.
 43. The method of claim 40, wherein the forming stepcomprises forming a transition metal salt into the oxygen barrier layeror a layer adjacent to the oxygen barrier layer of the packagingarticle.
 44. The method of claim 40, wherein the oxygen barrier layerfurther comprises a photoinitiator.
 45. The method of claim 40, whereinthe oxygen barrier layer further comprises an antioxidant.
 46. Themethod of claim 40, wherein the forming step further comprises formingan oxygen barrier layer in the packaging article, wherein the oxygenbarrier layer does not comprise a polyamide derived at least in partfrom a xylene diamine-based monomer.
 47. The method of claim 40, whereinthe forming step further comprises forming a structural layer in thepackaging article.
 48. The method of claim 40, wherein the forming stepfurther comprises forming an oxygen scavenging layer in the packagingarticle.
 49. The method of claim 40, wherein the forming step furthercomprises forming the packaging article as a single layer flexiblearticle, a multilayer flexible article, a single layer rigid article, ora multilayer rigid article.